Copper complexes hydroxides

The anhydrous chloride is prepared by standard methods. It is readily soluble in water to give a blue-green solution from which the blue hydrated salt CuClj. 2H2O can be crystallised here, two water molecules replace two of the planar chlorine ligands in the structure given above. Addition of dilute hydrochloric acid to copper(II) hydroxide or carbonate also gives a blue-green solution of the chloride CuClj but addition of concentrated hydrochloric acid (or any source of chloride ion) produces a yellow solution due to formation of chloro-copper(ll) complexes (see below). 

This example of the copper ion-hydroxide-ammonia system clearly demonstrates how complexation effects can either increase or decrease the solubility of a species of interest, and how such effects can be manipulated at the whim of the formulator. 

A hydroxoaqua copper complex containing N, N, N, A -tetramethyl-1,2-diamino-ethane (250) is an excellent catalyst for the hydrolysis of sarin, O-isopropyl methylphosphonofluoridate (251), and diethyl p-nitrophenyl phosphate (252 R = Et). The mechanism of the reaction probably involves bound hydroxide attacking the phosphoryl group with concomitant electrophilic catalysis by copper. 

Copper (II) salts have been found to be inactive as catalysts for the reaction with the exception of the copper (II) carboxylates which are considerably less reactive. In addition, the polymerization of 2.6-xylenol in pyridine with copper (II) acetate as catalyst appears to terminate before high molecular weight polymers are formed. However, treatment of an amine complex of a copper (II) salt with an equivalent of a strong gives the active catalyst. Similarly, although copper (II) hydroxide in pyridine is inactive as a catalyst, treatment with an equivalent of hydrogen chloride generates the active catalyst. Hence it can be concluded that the active catalyst is a basic salt (XV). 

The most interesting feature of this method, reviewed by Stepanov,62 is the ease with which the halogen atom is replaced by a hydroxyl group during the metallization process. This was first observed as long ago as 1931 when Delfs63 obtained the copper complex of 2-(2-hydroxy-naphthyl-l-azo)phenol-4-sulfonic acid (47) by heating an aqueous solution of l-chloro-2-(2-hydroxynaphthyl-l-azo)benzene-4-sulfonic acid (48), copper sulfate, sodium hydroxide and ammonia at 80 °C for 1 hour. 

Copper complex formation. Add a few drops of aqueous copper(n) sulphate solution to an aqueous solution of the amino acid. A deep blue coloration is obtained. The deep blue copper derivative may be isolated by boiling a solution of the amino acid with precipitated copper(n) hydroxide or with copper(n) carbonate, filtering and concentrating the solution. These blue complexes are coordination compounds of the structure ... 

In light of the accepted mechanism for cytochrome P-450 (97-100), a superoxo-Cu(II) intermediate is further reduced, leading to dioxygen activation. Accordingly, a monomeric peroxo or hydroperoxo copper(II) complex serves as a synthetic model for these intermediates of copper-containing monooxygenases. However, no well-characterized complexes of these types are available to date. Formation of a monomeric hydroperoxo or acylperoxo complex was reported to occur when a trans-/u-l,2-peroxo complex, [(Cu(TPA))2(02)]z+, was treated with H+ or RC(O)+, but no details of the structures and properties of the complexes were provided (101). A related complex, a monomeric acylperoxo cop-per(II) complex, was synthesized (102). Low-temperature reaction of a dimeric copper(II) hydroxide complex, [Cu(HB(3,5-iPr2pz)3)]2(OH)2, with 2 equivalents of m-CPBA (3-chloroperoxybenzoic acid) yielded a monomeric acylperoxo complex whose structure was characterized by... 

The only pentosans which have been studied to any great extent are the xylans. These can be obtained from all lignified cell membranes by extraction with 5% sodium hydroxide solution after lipids, pectic materials etc. have been removed. The conditions necessary to avoid degradation during isolation have been outlined.2 Early structural determinations indicated that arabinose was present as a non-reducing end-group in a branched molecule which had a chain-length of 18-20 D-xylo-furanose residues.27 It has been shown recently, however, that the xylan from esparto holocellulose can be purified free of arabinose after several re-precipitations of the copper-complex.28... 

Copper and its alloys are resistant to alkalies with the exception of ammonium hydroxide and cyanides. Ammonium ions promote stress-corrosion cracking of copper and its alloys. Ferric and stannic salts are aggressive towards copper alloys. Ammonia and cyanide ions form tetramine copper and tetracyano copper complexes in ammonia and cyanide solutions, respectively. 

In the presence of a solution of tartaric acid or of citric acid, copper(II) hydroxide is not precipitated by solutions of caustic alkalis, but the solution is coloured an intense blue. If the alkaline solution is treated with certain reducing agents, such as hydroxylamine, hydrazine, glucose, and acetaldehyde, yellow copper(I) hydroxide is precipitated from the warm solution, which is converted into red copper(I) oxide Cu20 on boiling. The alkaline solution of copper(II) salt containing tartaric acid is usually known as Fehling s solution it contains the complex ion [Cu(COO.CHO)]2. ... 

Figure 2. Titration data for complexation of copper by hydroxide. All solutions contained iOmM KNO3 (A) i.O/xM CuSOj, (O) 2.5/xM CuSO (first run), and 2.5/xM CuSO (second run). Curve calculated according to hydroxo constants determined in this work (Table I).

The recorded differences in adsorption capability indicate a different mechanism of interaction between the carbon surface and the ionic metal species pre.sent in the aqueous solution (aqua and hydroxy complexes, hydroxide ions, and electronegative complexes). To discover the state of the adsorbed. species, some independent measurements of the surface layer of adsorbent were carried out. The selected carbon samples were studied by the XPS method in powdered form following copper uptake (Figs. 42 and 43). Several peaks attributable to carbon, oxygen, nitrogen, and copper were present. The XPS survey spectra of the initial modified carbons (before adsorption) were discussed in the previous section. The surface elemental composition estimated from XPS data for modified D43/1 car-... 

Problem In order to show further phenomena on the structure of complexes and complex equilibria, it should be shown that the central ion is solidly bound to the ligands and is not solely present in the solution, in the stable tetra ammine copper complex. In order to do this, an iron nail is dipped into the complex solution, respectively, diluted sodium hydroxide solution is added and this is compared to regular copper sulfate solution the iron nail does not show the copper deposit as usual, no precipitation of the copper hydroxide is deposited. The copper sulfate solution should be interpreted in comparison to the complex solution as a solution with free Cu2 + (aq) ions or very instable aqueous copper complexes. With the explanation of the copper deposit on iron a cross-linkage to redox reactions (see Chap. 8) is possible. 

An equimolar mixture of the Schiff base and cupric acetate monohydrate in ethanol was heated under reflux for 2 h. The ethanol was evaporated in vacuo and the dark green residue was dissolved in toluene. The toluene solution was treated with aqueous sodium hydroxide to complete complex formation. Removal of the toluene followed by trituration in methanol induced crystallization of the copper complex as a bluish green mass. Filtration of the solid followed by drying in vacuo gave a pure sample, [a]546 -1-1040 ° (c 0.087, benzene), mp 186-188 °C (dec), in 77% yield based on the Schiff base. The magnetic susceptibility i was 0,86 B.M. For X-ray crystallography, see [14]. 

Masking can be achieved by precipitation, complex formation, oxidation-reduction, and kinetically. A combination of these techniques may be employed. For example, Cu " can be masked by reduction to Cu(I) with ascorbic acid and by complexation with I . Lead can be precipitated with sulfate when bismuth is to be titrated. Most masking is accomplished by selectively forming a stable, soluble complex. Hydroxide ion complexes aluminum ion [Al(OH)4 or AlOa"] so calcium can be titrated. Fluoride masks Sn(IV) in the titration of Sn(II). Ammonia complexes copper so it cannot be titrated with EDTA using murexide indicator. Metals can be titrated in the presence of Cr(III) because its EDTA chelate, although very stable, forms only slowly. 

The glucomannans obtained in this way are usually pure enough for structural investigations. Minor proportions of a contaminating xylan are readily removed by one or two purifications by way of the insoluble complex of the glucomannan with barium hydroxide. The copper complex may also be used for this purpose. i - ... 

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